I had a similar living room size (24' X 12) and had run Acoustic Research 12 gage speaker "wire" under the floor of my living room. The people at both Kimber Kable, Audioquest and TAS suggested it was better to use short speaker runs and long interconnects than vice versa. When my Marantz 2270 (70 wats rms) receiver gave up the ghost, I bought 2 monoblock Nuforce amps (190 RMS) and set them up right behind my speakers, thus 14 inch speaker cables and long interconnects from my pre-amp. Although the major improvements in clarity and musicality was undoubtly largely attributable to my Nuforce 9V2SE amps (they're fantastic!) I'm sure the new configuration definitely contributed as well, as I have since been able to confirm when friends switched configuration in their systems. Because speaker cable is generally more expensive than interconnect cable and given the length of speaker cable involved in your setup, the savings could free up some dollars for improved cabling. I'm investigating Harmonitech/Lessloss/Kubala-Sosna alternatives. Good luck with your choices.
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